The compounds of formula I are described as interphenylene-11,12-secoprostaglandins. The compounds are named in this manner since they have certain structural features in common with interphenylene analogs of the natural prostaglandins. The structure of the present compounds differ from such interphenylene analogs in that they lack the cyclopentane ring characteristic of the natural prostaglandins.
The prostaglandins constitute a class of highly functionalized C.sub.20 fatty acids. They have been shown to occur extensively in low concentrations in mammalian tissues where they are both rapidly anabolized and catabolized and to exhibit a broad spectrum of pharmacological activities including prominent roles in (a) functional hyperemia, (b) the inflammatory response, (c) the central nervous system, (d) transport of water and electolytes, and (e) regulation of cyclic AMP. Further details concerning the prostaglandins can be found in recent reviews of their chemistry [J. E. Pike, Fortschr. Chem. Org. Naturst., 28, 313 (1970) and G. F. Bundy A. Rep. in Med. Chem., 7, 157 (1972)]; biochemistry [J. W. Hinman, A. Rev. Biochem., 41, 161 (1972)]; pharmacology [J. R. Weeks, A. Rev. Pharm., 12, 317 (1972)]; physiological significance [E. W. Horton, Physiol. Rev., 49, 122 (1969)]; and general clinical application [J. W. Hinman, Postgrad. Med. J., 46, 562 (1970)].
The potential application of natural prostaglandins as medicinally useful therapeutic agents in various mammalian disease states is obvious but suffers from three formidable major disadvantages, namely, (a) prostaglandins are known to be rapidly metabolized in vivo in various mammalian tissues to a variety of metabolites which are devoid of the desired original biological activities, (b) the natural prostaglandins are inherently devoid of biological specificity which is requisite for a successful drug, and (c) although limited quantities of prostaglandins are presently produced by both chemical and biochemical processes, their production cost is extremely high; and consequently, their availability is quite restricted.
Our interest has, therefore, been to synthesize novel compounds structurally related to the natural prostaglandins, but with the following unique advantages: (a) simplicity of synthesis leading to low cost of production; (b) specificity of biological activity; and (c) enhanced metabolic stability so that activity can be obtained on oral as well as parenteral administration.
These advantages have been realized in the compounds of this invention. Certain of the compounds exhibit renal vasodilatory activity on oral administration and, therefore, are useful for the treatment of patients with renal impairment. Included in this group are patients with hypertension, renal failure, congestive heart failure, glomerulonephritis, uremia, and chronic renal insufficiency. The compounds of this invention by virtue of their renal vasodilatory activity improve renal function both when used alone or in conjunction with other renal agents. An example of a compound with high renal vasodilatory activity is 4-[4-acetyl-7-(1-hydroxycyclohexyl)heptyl]benzoic acid.
In addition to their activity as renal vasodilators, many compounds of this invention have useful adjunctive properties which give them added utility for the treatment of renal disease. Such properties include diuretic, saluretic, antihypertensive, and immunoregulant activities.
With regard to the indications that the compounds of this invention can be useful in therapy as regulators of the immune response, it can be stated that the basis for their activity in this area is their ability to stimulate cyclic-AMP formation in cells. Agents, including the E prostaglandins, that increase cellular cyclic-AMP concentration, interfere with the cell-mediated immune response by inhibiting lymphocyte expression in response to antigen, by inhibiting release of pathological mediators from sensitized lymphocytes, and by inhibiting the killing of target cells by such lymphocytes. Various assays which depend upon the measurement of some function of the immunologically competent lymphocyte can be used to demonstrate that the prostaglandin analogs of this invention are similarly active. For example, the release of lymphokines (proteins that are agents of inflammation and tissue destruction) from sensitized lymphocytes in culture is strongly inhibited by these analogs in low concentrations. Thus, it is apparent that the compounds of this invention are applicable to the treatment of those autoimmune diseases in whose pathogenesis a cell-mediated immune reaction is involved. Such diseases range from contact dermatitis to such chronic destructive diseases as rheumatoid arthritis and possibly multiple sclerosis and systemic lupus erythematosus. An example of a compound which is an effective regulator of the immune response is 4-(4-acetyl-8-hydroxytridecyl)benzoic acid.
Since the rejection of organ grafts is considered to be predominantly a cell-mediated immune phenomenon, a further area of usefulness of the compounds of this invention is in the prevention of transplant rejection.
The compounds of this invention can be administered intravenously, subcutaneously, intramuscularly, orally, rectally, or by aerosolization in the form of sterile implants for long action. They can be formulated in any of a number of pharmaceutical compositions and non-toxic carriers to this end.
The pharmaceutical compositions can be sterile, injectable suspensions or solutions, or solid orally-administrable, pharmaceutically acceptable tablets or capsules; the compositions can also be intended for sublingual administration, or for suppository use. It is especially advantageous to formulate compositions in dosage unit forms for ease and economy of administration and uniformity of dosage. "Dosage unit form" as a term used herein refers to physically discrete units suitable as unitary dosages for animal and human subjects, each unit containing a predetermined quantity of active material calculated to produce the desired biological effect in association with the required pharmaceutical means.
Illustratively, a sterile injectable composition can be in the form of aqueous or oleagenous suspensions or solutions.
The sterile injectable composition can be aqueous or oleagenous suspension or solution. Suspensions can be formulated according to the known art using suitable dispersing and wetting agents and suspending agents. Solutions are similarly prepared from the salt form of the compound. For the laboratory animals, we prefer to use incomplete Freund's adjuvant or sterile saline (9%) as carrier. For human parenteral use, such as intramuscularly, intravenously, or by regional perfusion, the diluent can be a sterile aqueous vehicle containing a preservative; for example, methylparaben, propylparaben, phenol, and chlorobutanol. The aqueous vehicle can also contain sodium chloride, preferably in an amount to be isotonic; as well as a suspending agent, for example, gum arabic, polyvinyl pyrrolidone, methyl cellulose, acetylated monoglyceride (available commercially as Myvacet from Distillation Products Industry, a division of Eastman Kodak Company), monomethyl glyceride, dimethyl glyceride, or a moderately high molecular weight polysorbitan (commercially available under the tradenames Tween or Span from Atlas Powder Company, Wilmington, Delaware). Other materials employed in the preparation of chemotherapeutic compositions containing the compound may include glutathione, 1,2-propanediol, glycerol, and glucose. Additionally, the pH of the composition is adjusted by use of an aqueous solution such as tris(hydroxymethyl)aminomethane (tris buffer).
Oily pharmaceutical carriers can also be used, since they dissolve the compound and permit high doses. Many oily carriers are commonly employed in pharmaceutical use, such as, for example, mineral oil, lard, cottonseed oil, peanut oil, sesame oil, or the like.
It is preferred to prepare the compositions, whether aqueous or oils, in a concentration in the range of from 2-50 mg./ml. Lower concentrations require needless quantities of liquid. Higher concentrations than 50 mg./ml. are difficult to maintain and are preferably avoided.
Oral administration forms of the drug can also be prepared for laboratory animals or human patients provided that they are encapsulated for delivery in the gut. The drug is subject to enzymatic breakdown in the acid environment of the stomach. The same dosage levels can be used as for injectable forms; however, even higher levels can be used to compensate for biodegradation in the transport. Generally, a solid unit dosage form can be prepared containing from 0.5 mg. to 25 mg. active ingredient.
Whatever the mode of administration, doses in the range of about 0.10 to 20 milligrams per kilogram of body weight administered one to four times per day are used, the exact dose depending on the age, weight, and condition of the patient, and the frequency and route of administration.
The low cost and ready accessibility of the compounds of this invention make them particularly promising for applications in veterinary medicine in which field their utilities are comparable to those in human medicine.